1. Field of the Invention
The invention generally relates to a printing machine, or press having a sheet feeder, and more specifically, to a device for controlling feeder blowing air and feeder suction air in a sheet feeder of a printing machine, or press. In general, printing presses are configured to handle large quantities of sheets of printing stock supplied in the form of a stack. For this purpose, sheet feeders which utilize air currents have been developed for repeatedly separating single sheets from a stack of sheets and initiating transport of the separated single sheets into the printing press. Such sheet feeders can utilize a blowing jet of air to fan the uppermost sheets of the stack, while a suction device can be provided to then suck the uppermost sheet thereto, and also to initiate movement of the sheet attached thereto into the printing press. The air suction and supply are generally controlled by a control device, which control device generally comprises respective valves for each of the feeder and blower air.
2. Background Information
A known embodiment of such a device is disclosed by German Laid Open Patent Application No. 39 31 995 A1, which corresponds to U.S. Pat. No. 5,068,876. This known embodiment provides two separate rotary valves for controlling the air, and each valve is individually controlled via an electromagnet. With this embodiment the rotary travel of an individual valve body may be manually adjusted via a rotary-travel limiter. Furthermore, fanning air supplied to the sheet feeder can also be manually adjusted via an adjusting screw so that the pressman does not have any exact adjusting values at hand, or in other words, so that the pressman does not have to remember the adjustment values that are input through the control.